The prevalence of hypertension in developed countries is about 20% of the adult population, rising to about 60-70% of those aged 60 or more. Hypertension is associated with an increased risk of stroke, myocardial infarction, atrial fibrillation, heart failure, peripheral vascular disease and renal impairment. Despite the large number of anti-hypertensive drugs available in various pharmacological categories, additional agents useful for the treatment of hypertension are still needed.
Vascular endothelial cells secrete nitric oxide (NO). This acts on vascular smooth muscle cells and leads to the activation of guanylate cyclase and the accumulation of cyclic guanosine monophosphate (cGMP). The accumulation of cGMP causes the muscles to relax and the blood vessels to dilate, leading to a reduction in blood pressure. The cGMP is inactivated by hydrolysis to guanosine 5′-monophosphate (GMP) by a cGMP-specific phosphodiesterase. One important cGMP-phosphodiesterase has been identified as phosphodiesterase type 5 (PDE5). Inhibitors of PDE5 decrease the rate of hydrolysis of cGMP and so potentiate the actions of nitric oxide.
Improved drug therapies for the treatment of subjects suffering from or susceptible to a cardiovascular condition are desirable. In particular, there still is a need for a new class of PDE-5 inhibitors for treating cGMP-mediated conditions and corresponding drug therapies.